TRAINS are being cancelled and delayed across the Southern Rail and Thameslink network this morning.

Rail chiefs have warned of "major disruption" due to "overrunning engineering works at several locations".

They say problems are likely to continue until noon.

Southern said in a statement: "Following planned weekend engineering works over running, all lines have re-opened in the London Victoria area.

"Additionally, a freight train is currently blocking the line in the Haydons Road area.

"This train was supposed to cross over onto the Wessex route earlier this morning but has been unable to due to overrunning engineering works in the Surbiton area.

"Due to no alternative routes being available for the train to take the southbound line is currently blocked.

"Most planned engineering work by Network Rail happens overnight, at weekends and on bank holidays, as this minimises disruption to passengers whilst also keeping engineers safe.

"Sometimes bad weather, machinery failure or unexpected complications can cause works to overrun.

"When an issue does occur, the train operators work closely with Network Rail to quickly assess the situation and to complete remaining repair works, so train services can be restored as quickly as possible."